This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-064593, filed Mar. 11, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a manufacturing method of a semiconductor device, and, particularly to improvements in the oxidation resistance and a property as diffusion barrier of formed Cu wiring.
Along with the development of finer miniaturization and more large-scaled integration of semiconductor devices, more miniaturized and multilayered metal wiring has been developed. Al alloy has been used as a miniaturized metal wiring material so far. However, when Al alloy is used, there has been a problem that the wiring resistance is increased, and the electro-migration resistance is degraded. Recently, Cu has been paid attention as a multi-layered wiring material.
However, wiring using Cu is easily oxidized in an oxidizing atmosphere such as deposition of interlayer insulation films, and separation of resists. Cu is diffused into interlayer insulation films unless the wiring surface is covered with suitable barrier metal. The diffusion of Cu into the interlayer insulation films causes degradation of the characteristics of MOS elements, as Cu becomes a life time killer of Si devices.
Then, when wiring using Cu is put to practical use, a method of covering the wiring surface with a protection film has been proposed to prevent the diffusion and the oxidation of Cu. A method of forming p-SiN on the wiring surface and the whole surface of insulation films, or a method of selectively forming a barrier layer only on the upper wiring surface has occurred to us for a method of covering the Cu wiring surface.
However, the relative dielectric constant of p-SiN used for surface covering is large (about 7). And, it covers not only the upper wiring surface, but also the whole surface of the insulation films. Therefore, even with a material having a low dielectric constant for interlayer insulation films, it is impossible to reduce the capacitance of highly pitched wiring.
On the other hand, when a barrier layer is selectively formed only on Cu, there are problems such as not enough barrier property and uniformity of the formed barrier layer. Especially, the barrier property is reduced when the barrier layer is formed away from the wiring surface. And, there is conceived of a method for a process selectively to form a barrier layer only on Cu as described in the following: A barrier material such as Al is formed on a Cu wiring, and a reaction layer is formed by thermal processing. Then, Al, other than that on the Cu wiring, is etched with substances such as acid, and alumina is formed on the Cu wiring surface as a diffusion barrier by heat-treatment. However, the above method has had a problem that, when the reacted Al film is thick, enough acid resistance is obtained, but, Al is also diffused into the Cu wiring to increase the resistance. Moreover, when the reaction Al film is thin to prevent increasing the resistance, there has been a problem that the acid resistance is not enough, and the etching selectivity to etch the parts other than those on the wiring was not obtained.
As mentioned above, in conventional manufacturing methods of a semiconductor device, a method of forming p-SiN on the wiring surface, or a method of selectively forming a barrier layer on the wiring surface has occurred to us for covering the Cu wiring upper surface. However, there have been problems such as the increased wiring capacitance, and not enough barrier property and uniformity of the formed barrier layer.
The object of the present invention is to provide a manufacturing method of a semiconductor device having the reduced wiring capacitance and wiring resistance, and the good barrier and uniformity properties.
According to a first aspect of the present invention, the present invention provides a manufacturing method of a semiconductor device comprising the steps of: forming an insulation film on a substrate; selectively forming an etching mask on the insulation film; forming a trench by selective removal of the insulation film using the etching mask; forming a Cu wiring in the trench with at least some parts of the etching mask remained; forming a barrier material on the etching mask and the Cu wiring; having an eutectic reaction between the etching mask and the barrier material by heat-treatment of the barrier material in an atmosphere of nitrogen, and nitriding the barrier material on the Cu wiring to form a barrier layer against Cu diffusion and oxidation; and removing the barrier material selectively on the etching mask after eutectic reaction with the etching mask, and making the barrier layer remained selectively on the Cu wiring.
According to another aspect of the present invention, the present invention provides a manufacturing method of a semiconductor device comprising the steps of: forming an insulation film on a substrate; selectively forming an etching mask on the insulation film; forming a trench by selective removal of the insulation film using the etching mask; forming a Cu wiring in the trench with at least some parts of the etching mask remained; forming a barrier material on the etching mask and the Cu wiring; having an eutectic reaction between the etching mask and the barrier material by heat-treatment of the barrier material; removing the barrier material selectively on the etching mask after eutectic reaction with the etching mask, and making the barrier material remained selectively on the Cu wiring; and nitriding the barrier material remained, thereby to form a barrier layer selectively on the Cu wiring.
According to a still another aspect of the present invention, the present invention provides a manufacturing method of a semiconductor device comprising the steps of: forming an insulation film on a substrate; forming a trench by selective removal of the insulation film; forming a Cu wiring in the trench; forming, on the Cu wiring and the insulation film, a barrier material having higher binding energy with oxygen, and better oxidation resistance than that of Cu and better property as Cu diffusion than that of Cu; forming an alloy layer of Cu and the barrier material on the Cu wiring by heat-treatment of the barrier material; selectively removing the barrier material, other than that on the Cu wiring with acid treatment containing the barrier material; and forming a barrier layer by selective oxidation of the alloy layer through heat-treatment of the alloy layer remained on the Cu wiring in an atmosphere where Cu is deoxidized, and the barrier material is oxidized.
In the present invention, an etching mask used for forming a trench is made to remain at forming a Cu wiring; a Cu wiring is formed in the trench; a barrier material having different kinds of eutectic reactions by heat-treatment is formed on the Cu wiring and the etching mask; the barrier material on the Cu is selectively nitrided, or oxidized, using the difference reactions between the eutectic reaction with the Cu wiring and that with the etching mask by heat-treatment of the barrier material in an atmosphere of oxygen or nitrogen. Therefore, it is possible to reduce the wiring capacitance in comparison with the conventional case where the barrier material is formed not only on the Cu wiring, but also on the whole surface of the insulation film.
In another aspect of the present invention, the barrier material is formed in a self-aligning manner to form a barrier layer with good barrier property; it is easy selectively to eliminate the barrier material other than that on the Cu wiring with less dishing and the like. Therefore, it is possible to form the barrier layer with good uniformity and reduced wiring resistance.
In still another aspect of the present invention, a Cu wiring is formed; a barrier material having higher binding energy with oxygen, and better oxidation resistance and Cu diffusion barrier property than those of Cu is formed; an alloy layer is formed on the Cu wiring by heat-treatment; the barrier material, other than that on the Cu wiring, is selectively eliminated with acid treatment containing the barrier material, that is, for selective removal of the barrier material, acid having the barrier material is used for the processing as mentioned above. Thereby, the barrier layer may be formed in a self-aligning manner, and the etching selectivity to etch the parts other than those on the Cu wiring may be improved. The presence of the barrier material contained in the acid causes the difference in the electrode potential between the reaction layer and the non-reaction layer to improve the etching selectivity. Therefore, there is no need to secure the etching selectivity by thickening the barrier material, that is, only thin barrier layer may be required. Moreover, while securing the etching selectivity to etch the parts other than those on the Cu wiring layer, it may be possible to reduce diffusion of the barrier material, prevent increase in the resistance, and maintain the high barrier property as a result of secured etching selectivity.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.